The invention relates to a lubricant discharge device for controlled removal of lubricant from a bearing housing of an electric motor. Such a device typically comprises a cylinder arranged in close connection with a lubricant discharge opening situated in an end shield or a bearing cap of the electric motor. The lubricant that has flowed into the cylinder is discharged by means of a piston provided in the cylinder.
An axle in an electric motor is typically supported on the motor frame by at least two main bearings, which are usually located at each end of the motor frame. Lubricant is used to lubricate the bearings. For conducting the lubricant to the bearing, the frame of the electric motor is usually provided with a bearing housing placed in an end shield forming the end piece of the motor frame, to receive the lubricant conducted thereto via a lubricant conduit. The end of the lubricant conduit comprises a grease nipple, through which the lubricant is pressed into the lubricant conduit. The end shield is also provided with a lubricant discharge opening, via which the excess lubricant is able to leave the bearing housing. This lubricant discharge opening is closed by means of different closing means, such as a screw inserted into the opening, a plastic plug pressed into the opening, or a grease receiver placed at the mouth of the opening. In the most advanced arrangement a cylindrical lubricant discharge device is tightly arranged at the mouth of the discharge opening in the end shield or the bearing cap of the electric motor, and the cylinder of the device comprises a piston arranged inside the cylinder to draw out of there the lubricant that has flowed into the cylinder.
Controlled removal of extra lubricant from a bearing housing of an electric motor is particularly important in surroundings requiring a high level of purity, such as in food industry. It is important to prevent the lubricant from splashing to the surroundings via the lubricant discharge opening or via bearing packings of the motor axle. Also environmental protection regulations, which are becoming stricter and stricter, require that any leaking of lubricant to pollute the surroundings be prevented. Furthermore, it is important that the motor is leak-proof, i.e. it comprises no apertures that could easily remain open for example after maintenance, thus allowing dust and moisture into the bearing housing to possibly damage the bearing and the motor. Moreover, the enclosure class of the motor decreases if the motor frame comprises open apertures.
Such a prior art lubricant discharge device comprises a cylinder or a pipe arranged at the mouth of a lubricant discharge opening in an end shield or a bearing cap of an electric motor parallel to the surface thereof. The cylinder is tightly closed at the and near the lubricant discharge opening in the end shield. An openable plug protects the other end of the pipe, which is typically located at the edge of the end shield in the electric motor. Inside the pipe there is a piston that is moved by a rod-like arm connected to the piston. The device operates such that during inaction the piston is inserted into the closed pipe end so that additional lubricant flowing from the bearing housing of the motor to the cylinder is able to drain away to the side of the piston near the openable cylinder end, i.e. to the front of the piston. When the additional lubricant that has flowed into the cylinder is to be removed therefrom, a plug situated at the openable end of the cylinder is opened and the piston is pulled out of the cylinder by an arm provided inside the cylinder and connected to the piston. The piston thus draws the lubricant with it, and the lubricant is then discharged via the open end of the cylinder and recovered.
However, the prior art lubricant discharge device disclosed above has problems that complicate controlled removal of lubricant. In the device, the lubricant that has gathered in the cylinder is discharged by pulling the piston out of the cylinder, so that the lubricant is released via the open cylinder end. Such an arrangement always requires the use of additional tools to recover the lubricant, since a large amount of the discharged lubricant adheres to the piston and must be scraped off. Furthermore, in the arrangement the cylinder head becomes dirty and must be cleaned by additional methods. The device also comprises several unconnected components, which might be lost or damaged, and the motor may thus become less leak-proof if for example the plug intended for the cylinder end is not reinstalled after the removal of the lubricant.
The prior art arrangement is thus difficult to use and therefore causes a risk of pollution to the environment of the motor. Also, when properly carried out, maintenance requires unnecessary stages of operation and a great deal of wasted time and also creates extra costs.
An objective of the present invention is to eliminate prior art drawbacks and to provide an improved arrangement for a lubricant discharge device of an electric motor.
This is achieved by an arrangement characterized by what is disclosed in the claims of the present invention. More precisely, the arrangement according to the invention is characterized in that the lubricant discharge device comprises a tubular element arranged closely at a lubricant discharge opening in a bearing housing of an electric motor, the element comprising a first end located substantially at the grease discharge opening of the bearing housing of the electric motor, and an opposite, second end situated substantially at the outer edge of an end shield in the electric motor. An opening is provided in the casing of the tubular element substantially close to the second end of the tubular element, and a closing means, such as a slide, is arranged inside the tubular element at the opening to open and close the opening. This closing means is arranged to open and close the opening such that the closing means moves a certain distance inside the tubular element. The aforementioned opening in the outer casing of the tubular element thus acts as a lubricant discharge opening to discharge the lubricant gathered inside the tubular element.
The preferred embodiments of the invention are disclosed in the dependent claims.
The tubular element is preferably a round cylinder. The tubular element can naturally also be triangular, quadrangular or the like. However, the shape of the closing means always corresponds to the shape of the tubular element. For the sake of simplicity, the tubular element will be hereinafter referred to as a cylinder regardless of its actual shape.
The outer circumference of the closing means approximately equals the inner circumference of the cylinder. The outer circumference of the closing means and the inner circumference of the cylinder casing thus form together a sealing in the area where they connect, when the clearance at the connecting surface is designed to be sufficiently small. At the edge near the piston, the outer surface of the closing means can preferably also comprise a groove, which is provided with a seal, such as an O ring, a metal ring or some other corresponding traction seal. A sealing is thus formed at the connecting surface between the closing means and the cylinder""s inner casing to prevent the lubricant from leaking uncontrollably out of the space reserved for it in the cylinder to pollute the environment.
Substantially in the middle of its diameter, the closing means comprises a through hole for inserting the arm section of the piston, arranged in the longitudinal direction of the closing means and equalling in size the diameter of the arm section. Thus, the piston is preferably able to move in the cylinder without the closing means restricting the piston movement outside the cylinder end near the closing means.
The outer surface of the closing means comprises a groove provided with a stop element, such as a locking ring, and the inner surface of the cylinder in turn comprises a groove arranged to receive the stop element. The stop element is thus arranged to fasten the closing means in place inside the tubular element. The width of the groove provided on the outer surface of the closing means is designed so that the groove allows the closing means to move a sufficient distance in the cylinder in order to open and close the lubricant discharge opening located near the cylinder end at the outer edge of the end shield in the electric motor. The closing means is thus able to move a distance equalling the groove width in the cylinder, restricted by the stop element, thus opening and closing the lubricant discharge opening.
The groove provided in the closing means can also comprise a spring element, the tension of which automatically closes the opening by moving the closing means thereto.
At the outer edge of the end shield in the electric motor, i.e. at the end of the piston arm opposite to the piston, the other end of the lubricant discharge device comprises a closing element consisting of a head and a thread. The thread is to be inserted into the cylinder and the head is intended to remain outside the opening provided at the end of the cylinder. When the closing element is inserted in place, the length of the thread of the closing element is preferably designed to push the closing means so as to close the lubricant discharge opening in the cylinder casing. An advantage is that the lubricant discharge opening closes whenever the closing element is properly inserted in place.
The opening situated in the outer casing of the cylinder can be preferably provided with a nipple or a pipe fitting, which in turn can be connected to a lubricant receiver, such as a box, a bag, a pipe or the like, for the duration of the discharge of lubricant. The arrangement according to the invention thus enables improved control of the lubricant discharge. Therefore lubricant can be discharged from the bearing housing and the cylinder so that no lubricant leaks to the environment, but all the lubricant can be efficiently collected to the lubricant receiver. This prevents the motor from getting dirty and the lubricant from splashing uncontrollably to the surroundings of the motor, while ensuring proper lubrication of the bearing. Furthermore, the sealing of the motor thus always corresponds to the requirements, for example the IP66 enclosure class, since the closing means can always be inserted in place in a simple manner.